Thomas Henry VC Crossfader VCA

Been working on this one for a little bit now :smiley:
Just finished it up today - may have to run another JLC order this week lolol.


Lookin’ snazzy! Excited to see this one.


I finished my build some time ago. The crossfader, unfortunately, is implemented backwards. Fortunately, I fixed that:

Unfortunately, the LED didn’t work after fixing the direction. Fortunately, with these faders the LED can be pulled out and put in the other way around.

Unfortunately, I could only bring the gain up to about half and then the sound would disappear. Fortunately, swapping in NE5532 op amps for TL072’s fixed that problem.


Hmmm I don’t have that problem with the gain on my build with 72’s.

The crossfade is backwards but I’ll probably just deal with it

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What does the ac/dc do

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I imagine it depends on the input level. I don’t even want to think about the possibility that I have dodgy TL072’s.

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i was gonna say too - I showed mine to cory last night and am not having any gain issues -
I did a little patch with wires as well but cut the traces and routed them to where they met the headers - so now A is left and B is right lol.

The gain thing is confusing tho!

I still can’t figure out what AC and DC does either lolol

Confused why your LED doesnt work with the fix lol
We musta done it differently

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When you switch it over to AC the signal flows through the added cap, cutting off frequencies below a certain threshold.

huh… lol

Phase reversal if you get too close to the rails would rather mean that they’re legit.

(the TL072 has an asymmetrical “common mode” input range of VCC–+4 V to VCC+, NE5532 is symmetrical)

(there’s a new TL07xH version that has a wider range and apparently a lot of other improvements, but haven’t seen them in the wild yet)